Control moment gyroscope arrays, reaction wheel arrays, and other such devices deployed onboard a satellite or other spacecraft for attitude adjustment purposes generate vibratory forces during operation. Vibration isolation systems are commonly employed to minimize the transmission of vibratory forces emitted from such attitude adjustment devices, through the spacecraft body, to any vibration-sensitive components (e.g., optical payloads) carried by the spacecraft. Vibration isolation systems commonly include a number of individual vibration isolators (typically three to eight isolators), which are positioned between the spacecraft payload and the spacecraft body in a multi-point mounting arrangement. The performance of a vibration isolation systems is largely determined by the number of isolators included within the system, the manner in which the isolators are arranged, and the vibration attenuation characteristics of each individual isolator. Vibration isolation system employing three parameter isolators, which behave mechanically as a primary spring in parallel with a series-coupled secondary spring and damper, provide superior attenuation of high frequency vibratory forces as compared to vibration isolation systems employing other types of passive isolators, such as viscoelastic isolators. The three parameter isolators are advantageously implemented as single degree of freedom (“DOF”) devices, which provide damping along a single longitudinal axis. An example of a single DOF, three parameter isolator is the D-STRUT® isolator developed and commercially marketed by Honeywell, Inc., currently headquartered in Morristown, N.J.
During spacecraft launch, exceptionally high impact loads can be transmitted to the isolators of the vibration isolation system. To protect the isolators from the high impact loads generated during spacecraft launch, spacecraft isolation systems are commonly equipped with a number of launch locks, which are positioned between the spacecraft and the payload support structure (e.g., a palette or bench) in parallel with the isolators. However, while generally effective at protecting the isolation from high impact loads during launch, the usage of launch locks is associated with a number of disadvantages. The usage of multiple launch locks adds additional part count, weight, and hardware cost to the spacecraft isolation system. Initial set-up and fine tuning of launch locks can be labor intensive resulting in higher labor costs and extended manufacturing schedules. As a still further drawback, launch locks are typically actuated utilizing pyrotechnic devices, which can be unreliable and which tend to produce undesirably high shock forces when detonated potentially disrupting the payload or spacecraft components. Finally, as launch locks shunt vibrational forces around the isolators directly between the spacecraft and payload, the usage of launch lock systems results in limited isolation of the payload during spacecraft launch.
It is thus desirable to provide embodiments of an isolator, such as a three parameter isolator, that can be tuned to provide optimal damping in disparate operational environments characterized by different loading conditions. Advantageously, such a dual mode isolator could be combined with a number of like isolators to produce a multi-point spacecraft isolation system capable of remaining active during both spacecraft launch and during on-orbit operation of the spacecraft. Embodiments of such a spacecraft isolation system could thus be implemented without launch locks and thereby overcome the above-listed limitations associated therewith. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.